1. Field of the Invention
The present invention relates to a nonaqueous ink composition for an ink jet and a method of manufacturing ink comprising the same, and more particularly, to a nonaqueous ink composition for an ink jet, which features excellent print quality and is capable of high-speed printing, and a method of manufacturing ink comprising the same.
2. Description of the Related Art
Among ink jet printing methods, non-impact printing is classified into continuous ink jet systems and drop-on demand (DOD) systems.
In continuous ink jet systems, when ink is emitted in a continuous stream, the direction of the ink emitted is adjusted by changing an electromagnetic field. In DOD systems, ink is broken up into fine droplets, and the droplets are expelled.
DOD systems are classified into thermal-bubble ink jet systems and piezoelectric ink jet systems. Thermal-bubble ink jet systems use the pressure produced by bursting bubbles of ink heated in a narrow flow path to fire the ink. In piezoelectric systems, electricity passing through piezoelectric elements causes physical distortions in the elements, in order to fire the ink. Piezoelectric systems use a relatively simple mechanism and can form high-quality images with high precision, and thus have recently been extensively applied to printed electronic circuit patterns and the like for industrial applications, as well as for home printers.
Recently, a piezoelectric ink jet printing technique requires high-frequency response in ink, for the purpose of increasing productivity per unit time through high precision and fast printing speeds. Therefore, more importance has been given to an ink jet which is capable of stably ejecting droplets, even at a high driving frequency of the head, which is essential for the enhancement of an ink jet apparatus and the realization of high-speed printing.
In particular, with the increase in the driving frequency of the head, ejected droplets easily form a satellite or a bent ligament. This phenomenon may lead to the printing of portions other than of ink droplet impact points, thereby having an adverse effect on the formation of a high-precision image.
Due to these factors, various attempts in the development of ink compositions ensuring ejection stability are ongoing.
There has been proposed an ink for an ink jet capable of high-speed printing, the ink containing a mixture of a glycol ether solvent and one type of polyhydric alcohol (Japanese Unexamined Patent Application Publication No. 2008-266537). Such proposed compositions use a large amount of diethylene glycol ethyl ether, diethylene glycol butyl ether, triethylene glycol ethyl ether, or triethylene glycol butyl ether as the glycol ether solvent. Thus, the odor coming from the ink at the time of ink ejection has become a problem. Moreover, the disclosed one type of polyhydric alcohol, too, may cause degradation of response to an ejection frequency due to the dispersion of droplets by a shear force from a flow path, resulting from the high-speed operation of the head.
There has been proposed another ink for high-speed printing with improved ejection stability which is an ink using a specific surfactant (Japanese Unexamined Patent Application Publication Nos. 2008-184567 and 2007-197675). However, the corresponding surfactants may cause contamination in the flow path of the ink jet head. Thus, with an increase in ejection driving frequency, the dispersion of droplets may increase and the ink may cause excessive wettability against a head nozzle surface, thereby bringing about some problems in the high-speed printing ink.
As for inks for a thermal-bubble ink jet capable of high-speed printing, there was proposed an ink containing water as a main component and a glycol humectant mixed with the water for the purpose of suppressing ink from drying on a nozzle surface (Japanese Unexamined Patent Application Publication Nos. 1996-157758 and 2004-300280). However, the maximum ejection frequency was about 15 kHz, and thus the frequency response characteristic was suboptimal.